Differentiation of adrenergic neuroblasts from cells originating in the neural crest occurs after proliferation, migration and localization of the cells. Our laboratory has shown previously that heterotypic interactions play a significant role in promoting differentiation of these cells. The appearance of catecholamines in crest cells grown on the chick chorioallantoic membrane required association with the somites and ventral portion of the neural tube. Our most recent work has shown that neural crest cells will differentiate independently into adrenergic neuroblasts in vitro. Differentiation was assessed using the formaldehyde-induced fluorescence technique of Falck and Hillarp to identity cells containing catecholamines. These observations question the importance of those heterotypic interactions shown by us and others to be necessary for adrenergic neuroblast differentiation. The research proposed here extends these in vitro observations into the following areas: (1) to biochemically identify the catechloamines synthesized in our cultures; (2) to study the role of Nerve Growth Factor in the de novo appearance of catecholamines; (3) to clarify the influence of the somites in promoting differentiation of crest cells grown on the chorioallantoic membrane; and (4) to examine factors important to the migration and localization of crest cells that coalesce to form spinal and sympathetic ganglia. Work is also planned to evaluate the relationship between uptake of exogenous catecholamines and the appearance of formaldehyde-induced fluorescence of crest cells grown in vitro. BIBLIOGRAPHIC REFERENCE: Cohen, A.M. and I.R. Konigsberg. 1975. A Clonal Approach to the Problem of Neural Crest Determination. Develop. Biol. 46:242-280.